US-12623996-B2 - Method for industrially producing dialkyl carbonate and diol

Abstract

The method for industrially producing a dialkyl carbonate and a diol, in which the dialkyl carbonate and the diol are continuously produced through a reactive distillation system of taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, comprising the steps of: continuously feeding the starting materials into a continuous multi-stage distillation column in which a homogeneous catalyst is present; carrying out reaction and distillation simultaneously in the column; continuously withdrawing a low boiling point reaction mixture containing the produced dialkyl carbonate in a gaseous form from an upper portion of the column; and continuously withdrawing a high boiling point reaction mixture containing the diol in a liquid form from a lower portion of the column, where the method satisfies specific requirements.

Inventors

• Hironobu Yamauchi

Assignees

• ASAHI KASEI KABUSHIKI KAISHA

Dates

Publication Date

20260512

Application Date

20211118

Priority Date

20210108

Claims (9)

1. 1 . A method for industrially producing a dialkyl carbonate and a diol in which the dialkyl carbonate and the diol are continuously produced through a reactive distillation system of taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, comprising: continuously feeding the starting materials into a continuous multi-stage distillation column in which a homogeneous catalyst is present; carrying out reaction and distillation simultaneously in the column; continuously withdrawing a low boiling point reaction mixture containing the produced dialkyl carbonate in a gaseous form from an upper portion of the column; and continuously withdrawing a high boiling point reaction mixture containing the diol in a liquid form from a lower portion of the column, wherein: (a) the continuous multi-stage distillation column comprises a tray column type distillation column which has a structure having a cylindrical trunk portion having a length L (cm) and an inner diameter D (cm) and having an internal therein, the internal being a tray having a plurality of holes, and the column further has a gas outlet at a column top portion or in the upper portion of the column near to the column top portion, a liquid outlet at a column bottom portion or in the lower portion of the column near to the column bottom portion, one or more first inlets provided in the upper portion and/or a middle portion of the column below the gas outlet, and one or more second inlets provided in the middle portion and/or the lower portion of the column above the liquid outlet, wherein: (1) the length L (cm) of the column satisfies Formula (1): 1 , 500 ≤ L ≤ 12 , 000 ; ( 1 ) (2) the inner diameter D (cm) of the column satisfies Formula (2): 1 ⁢ 2 ⁢ 0 ≤ D ≤ 3 , 000 ; ( 2 ) (3) the internal consists of three types of trays of upper, middle, and lower stages; (4) the starting material cyclic carbonate is continuously introduced into the continuous multi-stage distillation column through the one or more first inlets, and the upper stage is a stage above a stage of the inlet of an uppermost stage among the one or more first inlets, and a percentage of the number of trays of the upper stage is 1 to 10% of the total number of stages, (5) the starting material aliphatic monohydric alcohol is continuously introduced into the continuous multi-stage distillation column through the one or more second inlets, and the middle stage is a stage from a stage of the inlet of an uppermost stage among the one or more second inlets to the stage of the inlet of the uppermost stage among the one or more first inlets, and a percentage of the number of trays of the middle stage is 40 to 50% of the total number of stages; (6) the lower stage is a stage below the stage of the inlet of the uppermost stage among the one or more second inlets, and a percentage of the number of trays of the lower stage is 45 to 55% of the total number of stages; (7) in each stage tray of the lower stage, a percentage of active area calculated by Formula (i) below is 40 to 80%, and a percentage of open area calculated by Formula (ii) below is 1.0 to 5.0%: Percentage ⁢ ( % ) ⁢ of ⁢ active ⁢ area = area ⁢ ( cm 2 ) ⁢ of ⁢ active ⁢ area / area ⁢ ( cm 2 ) ⁢ of ⁢ tray × 100 ( i ) wherein the area of active area is an area of a compartment with a hole in a tray deck portion (ranging from a boundary of a minimum segment including all holes to 4 inches further outward), and the area of tray is an area of the tray deck portion, including the area of active area, but not including a downcomer portion; Percentage ⁢ ( % ) ⁢ of ⁢ open ⁢ area = area ⁢ ( cm 2 ) ⁢ of ⁢ open ⁢ area / area ⁢ ( cm 2 ) ⁢ of ⁢ active ⁢ area × 100 ( ii ) wherein the area of open area is the total area of all holes in the active area, and the area of active area is as defined in Formula (i); (8) in each stage tray of the upper and middle stages, the percentage of active area calculated by Formula (i) above is 40 to 80%, and the percentage of open area calculated by Formula (ii) above is 1.0 times or more the percentage of open area calculated by Formula (ii) above in each stage tray of the lower stage; and (9) the homogeneous catalyst consists of a mixture of an alkali metal and ethylene glycol, and a mass ratio of the alkali metal to the ethylene glycol (alkali metal/ethylene glycol) in the homogeneous catalyst is 0.05 to 0.5, and a catalyst concentration (in terms of alkali metal concentration) is 0.05 to 2.0% by mass of the cyclic carbonate fed to the distillation column.
2. 2 . The method according to claim 1 , wherein in the upper stage, a gas flow rate is 5,000 to 45,000 kg/hr, and a liquid flow rate is 1,000 to 15,000 kg/hr, in the middle stage, the gas flow rate is 5,000 to 30,000 kg/hr, and the liquid flow rate is 1,000 to 15,000 kg/hr, and in the lower stage, the gas flow rate is 5,000 to 20,000 kg/hr, and the liquid flow rate is 1,000 to 30,000 kg/hr.
3. 3 . The method according to claim 1 , wherein an amount of the dialkyl carbonate produced is 4.5 tons or more per hour.
4. 4 . The method according to claim 1 , wherein an amount of the diol produced is 2.5 tons or more per hour.
5. 5 . A continuous multi-stage distillation column for carrying out transesterification reaction between a cyclic carbonate and an aliphatic monohydric alcohol and distillation, wherein (a) the continuous multi-stage distillation column comprises: a cylindrical trunk portion having a length L (cm) and an inner diameter D (cm); a tray having a plurality of holes, provided inside the trunk portion as an internal; a gas outlet provided at a column top portion or in an upper portion of the column near to the column top portion; a liquid outlet provided at a column bottom portion or in a lower portion of the column near to the column bottom portion; one or more first inlets provided in the upper portion and/or a middle portion of the column below the gas outlet; and one or more second inlets provided in the middle portion and/or the lower portion of the column above the liquid outlet; (1) the length L (cm) of the column satisfies Formula (1): 1 , 500 ≤ L ≤ 12 , 000 ; ( 1 ) (2) the inner diameter D (cm) of the column satisfies Formula (2): 1 ⁢ 2 ⁢ 0 ≤ D ≤ 3 , 000 ; ( 2 ) (3) the internal consists of three types of trays of upper, middle, and lower stages; (4) the starting material cyclic carbonate is continuously introduced into the continuous multi-stage distillation column through the one or more first inlets, and the upper stage is a stage above a stage of the inlet of an uppermost stage among the one or more first inlets, and a percentage of the number of trays of the upper stage is 1 to 10% of the total number of stages, (5) the starting material aliphatic monohydric alcohol is continuously introduced into the continuous multi-stage distillation column through the one or more second inlets, and the middle stage is a stage from a stage of the inlet of an uppermost stage among the one or more second inlets to the stage of the inlet of the uppermost stage among the one or more first inlets, and a percentage of the number of trays of the middle stage is 40 to 50% of the total number of stages; (6) the lower stage is a stage below the stage of the inlet of the uppermost stage among the one or more second inlets, and a percentage of the number of trays of the lower stage is 45 to 55% of the total number of stages; (7) in each stage tray of the lower stage, a percentage of active area calculated by Formula (i) below is 40 to 80%, and a percentage of open area calculated by Formula (ii) below is 1.0 to 5.0%: Percentage ⁢ ( % ) ⁢ of ⁢ active ⁢ area = area ⁢ ( cm 2 ) ⁢ of ⁢ active ⁢ area / area ⁢ ( cm 2 ) ⁢ of ⁢ tray × 100 ( i ) wherein the area of active area is an area of a compartment with a hole in a tray deck portion (ranging from a boundary of a minimum segment including all holes to 4 inches further outward), and the area of tray is an area of the tray deck portion, including the area of active area, but not including a downcomer portion; Percentage ⁢ ( % ) ⁢ of ⁢ open ⁢ area = area ⁢ ( cm 2 ) ⁢ of ⁢ open ⁢ area / area ⁢ ( cm 2 ) ⁢ of ⁢ active ⁢ area × 100 ( ii ) wherein the area of open area is the total area of all holes in the active area, and the area of active area is as defined in Formula (i); and (8) in each stage tray of the upper and middle stages, the percentage of active area calculated by Formula (i) above is 40 to 80%, and the percentage of open area calculated by Formula (ii) above is 1.0 times or more the percentage of open area calculated by Formula (ii) above in each stage tray of the lower stage.
6. 6 . The method according to claim 2 , wherein an amount of the dialkyl carbonate produced is 4.5 tons or more per hour.
7. 7 . The method according to claim 2 , wherein an amount of the diol produced is 2.5 tons or more per hour.
8. 8 . The method according to claim 3 , wherein an amount of the diol produced is 2.5 tons or more per hour.
9. 9 . The method according to claim 6 , wherein an amount of the diol produced is 2.5 tons or more per hour.

Description

TECHNICAL FIELD The present invention relates to a method for industrially producing a dialkyl carbonate and a diol. BACKGROUND ART As a method for industrially producing a dialkyl carbonate and a diol, for example, Patent Document 1 proposes a method and an apparatus for producing a dialkyl carbonate and a diol in industrially large quantities (e.g., 2 tons or more of dialkyl carbonate per hour and 1.3 tons or more of diol per hour) through a reactive distillation system of taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, comprising continuously feeding the starting materials into a continuous multi-stage distillation column in which a homogeneous catalyst is present, and carrying out reaction and distillation simultaneously in the column, where they can be produced stably in a high yield for a prolonged period (e.g., 5,000 hours or more) with high selectivity and high productivity. LIST OF PRIOR ART DOCUMENTS Patent Document Patent Document 1: International Publication No. WO 2007/069514 SUMMARY OF INVENTION Problems to be Solved by Invention However, the method and apparatus described in Patent Document 1 sometimes don't have sufficient productivity of a dialkyl carbonate and a diol relative to the size of the apparatus. Accordingly, the problem to be solved by the present invention is to provide a specific method for industrially producing a dialkyl carbonate and a diol in industrially large quantities through a reactive distillation system of taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, comprising continuously feeding the starting materials into a continuous multi-stage distillation column in which a homogeneous catalyst is present, and carrying out reaction and distillation simultaneously in the column, where they can be produced with stable and even higher productivity (for example, 4.5 tons or more of dialkyl carbonate per hour and 2.7 tons or more of diol per hour) for a prolonged period (for example, 1,000 hours or more, preferably 3,000 hours or more, more preferably 5,000 hours or more) with stable high selectivity and high yield. Means for Solving Problems The present inventors have carried out intensive studies to solve the above-mentioned problems, and have found that, in producing a dialkyl carbonate and a diol in industrially large quantities with a column in the same length and inner diameter, by setting the length and inner diameter of the column, and the active area and the open area percentages of each stage tray in the column to a specific range, the dialkyl carbonate and the diol can be produced with stable and even higher productivity [e.g., 1.3 times or more (i.e., 4.5 tons or more of dialkyl carbonate per hour and 2.7 tons or more of diol per hour) the target value described in Patent Document 1 (2 tons or more of dialkyl carbonate per hour and 1.3 tons or more of diol per hour)] for a prolonged period (e.g., 1,000 hours or more, preferably 3,000 hours or more, and more preferably 5,000 hours or more) with stable high selectivity and high yield. As a result, the present inventors have arrived at the present invention. That is, the present invention is as follows. [1] A method for industrially producing a dialkyl carbonate and a diol in which the dialkyl carbonate and the diol are continuously produced through a reactive distillation system of taking a cyclic carbonate and an aliphatic monohydric alcohol as starting materials, comprising: continuously feeding the starting materials into a continuous multi-stage distillation column in which a homogeneous catalyst is present;carrying out reaction and distillation simultaneously in the column;continuously withdrawing a low boiling point reaction mixture containing the produced dialkyl carbonate in a gaseous form from an upper portion of the column; and continuously withdrawing a high boiling point reaction mixture containing the diol in a liquid form from a lower portion of the column, wherein:(a) the continuous multi-stage distillation column comprises a tray column type distillation column which has a structure having a cylindrical trunk portion having a length L (cm) and an inner diameter D (cm) and having an internal therein, the internal being a tray having a plurality of holes, and the column further has a gas outlet at a column top portion or in the upper portion of the column near to the column top portion, a liquid outlet at a column bottom portion or in the lower portion of the column near to the column bottom portion, one or more first inlets provided in the upper portion and/or a middle portion of the column below the gas outlet, and one or more second inlets provided in the middle portion and/or the lower portion of the column above the liquid outlet, wherein:(1) the length L (cm) of the column satisfies Formula (1): 1,500≤L≤12,000;(1)(2) the inner diameter D (cm) of the column satisfies Formula (2): 120≤D≤3,000;(3) the internal consists of three t